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AHuman RCT or meta-analysis
Neuropsychiatric

Enclomiphene

Enclomiphene Citrate

Enclomiphene (enclomiphene citrate) is an orally active, non-steroidal selective estrogen receptor modulator (SERM) — the pure trans-isomer of clomiphene citrate. It is not an anabolic steroid. It is used off-label to raise a man's own testosterone by blocking estrogen feedback at the hypothalamus/pituitary, which increases LH and FSH and stimulates the testes; unlike injected/topical testosterone, it does this while preserving sperm production. It has never received FDA approval (the developer's Androxal program failed to gain approval), so all human use is off-label or via compounding, and there are no long-term (multi-year) safety data. It manipulates the hormonal (HPT) axis and should only be used under a physician who runs bloodwork; documented and plausible harms include mood changes, altered libido, rising hematocrit (thicker blood), a theoretical class-based clot (venous thromboembolism) and visual-disturbance risk carried by triphenylethylene SERMs, and unknown long-term effects on bone and the cardiovascular system. Educational information only — not medical advice; consult a physician and obtain regular labs. 21+ only.

Clinical readoutAncillary · serm
Hepatic strainLow
CardiovascularNone
HPTA suppressionNone
Half-life
6.0 wk
Route
Oral
Evidence
A
Active
Oral once-daily dosing…
6.0 wk12.0 wk18.0 wk24.0 wk30.0 wk
Illustrative single-compartment washout · each mark = one half-life · t½ ≈ Not precisely characterized in the primary human trials. The parent enclomiphene (trans-isomer) is comparatively short-lived, in contrast to the cis-isomer zuclomiphene found in racemic clomiphene, which accumulates and predominates in serum (median zuclomiphene:enclomiphene ratio ~20:1 after >=6 weeks of clomiphene). Downstream hormonal effects (elevated LH and testosterone) persist for at least about one week after the last dose.
Pharmacology

Mechanism of action

Enclomiphene is the trans-isomer of clomiphene and acts as an estrogen-receptor antagonist at the hypothalamus and pituitary. By blocking estrogen's negative feedback centrally, it increases pulsatile GnRH and thereby raises pituitary luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Elevated LH stimulates testicular Leydig cells to produce endogenous testosterone, while FSH supports spermatogenesis — so testosterone rises through the man's own hypothalamic-pituitary-testicular (HPT) axis rather than being supplied exogenously. This is why it raises LH/FSH and preserves sperm counts, the opposite of exogenous testosterone, which suppresses LH/FSH and spermatogenesis. Separating out the cis-isomer (zuclomiphene), which is a longer-lived estrogen agonist, is intended to reduce estrogenic side effects.
Kinetics

Pharmacokinetics

Half-life

Not precisely characterized in the primary human trials. The parent enclomiphene (trans-isomer) is comparatively short-lived, in contrast to the cis-isomer zuclomiphene found in racemic clomiphene, which accumulates and predominates in serum (median zuclomiphene:enclomiphene ratio ~20:1 after >=6 weeks of clomiphene). Downstream hormonal effects (elevated LH and testosterone) persist for at least about one week after the last dose.

Active duration

Oral once-daily dosing was used in trials; biological effect on LH/testosterone outlasts the drug and persists roughly 7 days after cessation, with testosterone returning toward pretreatment values by about one month after stopping.

Route

Oral (tablet/capsule).

Metabolism & clearance

Hepatic metabolism (triphenylethylene SERM class), consistent with clomiphene-type compounds; detailed human clearance/excretion parameters for the isolated enclomiphene isomer are not well characterized in the published primary literature. PK data are provided for monitoring and washout reasoning and clinician discussion only — not for any test-evasion purpose.

For monitoring and washout planning, not drug-test evasion.

Reported effects

Physiological & performance effects

  • Raises serum total (and calculated free) testosterone into the normal range in men with secondary/functional hypogonadism
  • Increases LH and FSH (stimulates the endogenous HPT axis rather than suppressing it)
  • Preserves sperm concentration/spermatogenesis, unlike exogenous testosterone which suppresses it
  • Modestly raises estradiol as testosterone rises, but with a smaller estradiol increase than racemic clomiphene
  • Testosterone effect is comparable in magnitude to topical testosterone gel over 12-16 weeks in trials
  • Signals of a favorable effect on fasting glucose were reported in early development, but this is not an established clinical benefit
Safety

Adverse effects by system

Cardiovascular

No dedicated cardiovascular-outcome data exist. In a Phase II study enclomiphene did not significantly alter serum lipids. A theoretical class-based venous thromboembolism (clot) risk is attributed to triphenylethylene SERMs but has not been quantified for enclomiphene specifically; rising testosterone can also raise hematocrit. No adequate long-term human cardiovascular safety data.

Hepatic

No hepatotoxicity signal was reported in the controlled Phase II/III trials; enclomiphene is non-steroidal and not 17-alpha-alkylated. Dedicated liver-injury data are lacking, so hepatic safety is best described as not established rather than proven safe.

Endocrine / HPTA

Central mechanism: raises LH, FSH, testosterone and (modestly) estradiol. It stimulates rather than suppresses the HPT axis. Endocrine/estrogenic side effects (e.g., libido or mood changes) occur but were less frequent than with racemic clomiphene in a retrospective comparison.

Reproductive

Generally spermatogenesis-preserving (a relative advantage over exogenous testosterone). Increases estradiol modestly; gynecomastia and altered libido are possible (reported less often than with clomiphene). Effects on fertility are the basis for its use but long-term reproductive safety is not established.

Neuropsychiatric

Mood changes and reduced energy were documented, though at statistically lower rates than with clomiphene in a retrospective cohort. As a triphenylethylene SERM, mood alteration and (rarely) depressive symptoms are plausible; men with pre-existing mood disorders warrant caution.

Renal

No specific renal adverse effects were identified in the retrieved human literature; renal safety is essentially uncharacterized (no adequate data).

Hematologic

Because it raises endogenous testosterone, hematocrit can increase (polycythemia risk); in a retrospective cohort the median hematocrit change on enclomiphene was ~0%, but individual increases occur and hematocrit should be monitored.

Dermatologic

No distinct dermatologic adverse effect was identified in the retrieved human literature (no adequate data).

Recovery

HPTA suppression & recovery

Suppression: Does not suppress the HPT axis — it stimulates it. Enclomiphene raises LH, FSH and endogenous testosterone rather than shutting the axis down.

Because enclomiphene works by driving the HPT axis, it does not cause the axis suppression seen with exogenous androgens; hormonal effects wane within about a week of stopping and testosterone drifts back toward baseline by roughly one month. It is a single agent (single-SERM); dual-SERM protocols are out of scope and not described here. Any use for HPT-axis or fertility support, and any recovery plan, is variable between individuals and should be directed by an endocrinologist with serial bloodwork.

Bloodwork & vitals

Monitoring

Recommended labs & checks
Total and free testosteroneLH and FSHEstradiolComplete blood count / hematocrit (polycythemia surveillance)Comprehensive metabolic panel including liver enzymesLipid panelPSA in age-appropriate men before and during therapySemen analysis where fertility preservation is a goal

Cadence: Baseline before starting, an early recheck at roughly 4-12 weeks to confirm response and screen for rising hematocrit/estradiol, then periodically (e.g., every 3-6 months) while continuing, under a physician's direction.

Warning signs — seek care
  • Leg swelling/pain, chest pain, shortness of breath, or sudden severe headache (possible clot) — seek emergency care
  • New or worsening visual disturbances (blurring, floaters, light sensitivity) — stop and seek care
  • Significant mood changes, depression, or agitation
  • Symptoms of thickened blood: headaches, flushing, visual changes, dizziness
  • Breast tenderness or enlargement (gynecomastia)
  • Any severe or persistent adverse symptom — discontinue and consult a clinician
Do not use if

Contraindications

  • Not for use in women, and absolutely contraindicated in pregnancy (SERM/clomiphene class is a known teratogen)
  • Personal or high-risk history of venous thromboembolism (DVT/PE) or other thrombophilic states, given the SERM class clot concern
  • Pre-existing erythrocytosis/polycythemia (elevated hematocrit) that could be worsened by rising testosterone
  • Known hypersensitivity to clomiphene/enclomiphene
  • History of significant visual disturbances associated with SERM/clomiphene use
  • Untreated or suspected hormone-related concerns (e.g., prostate or breast pathology) without physician evaluation; primary (testicular-failure) hypogonadism, where a central-acting agent is not expected to work
  • Use without medical supervision and periodic laboratory monitoring
Combinations

Interaction profile

  • MajorWith another SERM: Blood / clotting
  • ModerateWith an aromatase inhibitor: Hormonal
  • ContraindicatedWith DNP: Additive cardiovascular strain

Check a specific combination in the interaction checker.

Harm reduction

Reducing harm & when to stop

  • This compound is not FDA-approved and has no long-term (multi-year) human safety data; treat any use as experimental and physician-supervised.
  • Do not use without baseline and follow-up bloodwork (testosterone, LH, FSH, estradiol, CBC/hematocrit, liver enzymes, lipids, and age-appropriate PSA).
  • Because it raises your own testosterone, hematocrit can climb — monitor CBC and stop/seek care if blood becomes too thick (headaches, flushing, visual changes).
  • Stop and seek emergency care for signs of a blood clot (leg swelling/pain, chest pain, shortness of breath) or sudden severe headache — a recognized class concern for SERMs.
  • Stop and seek care for new visual disturbances, which are associated with the clomiphene/SERM class.
  • Watch for and report mood changes or depression; men with pre-existing mood disorders should be especially cautious.
  • This is a single agent — do not combine SERMs; dual-SERM protocols are out of scope. Any HPT-axis, fertility, or recovery use should be directed by an endocrinologist.
  • Never use in women or if pregnancy is possible in a partner relying on it — the class is teratogenic.
  • Dose ranges reported in the literature (roughly 6.25-25 mg daily) are described only to contextualize the studied risks; this is not a dosing recommendation, and no 'optimal' dose is endorsed.
  • This is educational information, not medical advice, and does not create a doctor-patient relationship.
Evidence

Citations (10)

Every clinical claim above is tied to a primary source. Overall evidence grade A — graded to the best available evidence for its core claims.

  1. 01

    Enclomiphene is the trans-isomer of clomiphene, a non-steroidal estrogen-receptor antagonist that raises endogenous testosterone by increasing LH/FSH via central estrogen-receptor blockade.

    ReviewPMID 19204885 ↗

  2. 02

    In men with secondary hypogonadism, enclomiphene increased serum total testosterone into the normal range and raised LH and FSH; effects on LH and testosterone persisted at least one week after stopping, and it did not significantly affect lipids, TSH, ACTH, cortisol or bone markers in a Phase II study.

    RCTTestosterone Restoration by Enclomiphene Citrate in Men with Secondary Hypogonadism: Pharmacodynamics and Pharmacokinetics.PMID 23875626 ↗

  3. 03

    In a randomized Phase II trial, enclomiphene raised morning testosterone, estradiol, LH and FSH comparably to topical testosterone gel while conserving sperm counts (secondary hypogonadism).

    RCTEnclomiphene citrate stimulates testosterone production while preventing oligospermia: a randomized phase II clinical trial comparing topical testosterone.PMID 25044085 ↗

  4. 04

    In two parallel double-blind, placebo-controlled Phase III trials in overweight men with secondary hypogonadism, enclomiphene raised total testosterone, LH and FSH and maintained sperm concentration in the normal range over 16 weeks, whereas testosterone gel raised testosterone but markedly reduced spermatogenesis.

    RCTOral enclomiphene citrate raises testosterone and preserves sperm counts in obese hypogonadal men, unlike topical testosterone: restoration instead of replacement.PMID 26496621 ↗

  5. 05

    In a randomized Phase IIB comparison, enclomiphene raised testosterone and sperm counts via increases in LH/FSH; testosterone fell back toward pretreatment values about one month after stopping treatment.

    RCTOral enclomiphene citrate stimulates the endogenous production of testosterone and sperm counts in men with low testosterone: comparison with testosterone gel.PMID 23530575 ↗

  6. 06

    A systematic review and meta-analysis found enclomiphene citrate 12.5-25 mg daily significantly increased testosterone (pooled mean difference ~7.5 nmol/L) in men with obesity-related functional androgen deficiency, with no unexpected safety findings over 1.5-4 months.

    Meta-analysisSelective modulation of estrogen receptor in obese men with androgen deficiency: A systematic review and meta-analysis.PMID 36604313 ↗

  7. 07

    In a retrospective cohort, enclomiphene produced a testosterone increase similar to clomiphene but with a smaller rise in estradiol and statistically fewer adverse events (decreased libido, reduced energy, mood changes); median hematocrit change was ~0%.

    CohortSafety and efficacy of enclomiphene and clomiphene for hypogonadal men.PMID 39434750 ↗

  8. 08

    The parent enclomiphene isomer is comparatively short-lived, whereas the cis-isomer zuclomiphene accumulates and predominates in serum during chronic clomiphene therapy (median zuclomiphene:enclomiphene ratio ~20:1).

    CohortSerum levels of enclomiphene and zuclomiphene in men with hypogonadism on long-term clomiphene citrate treatment.PMID 27511863 ↗

  9. 09

    SERMs including enclomiphene citrate appear effective for improving serum testosterone in hypogonadal men with symptom improvement comparable to testosterone replacement, based on RCTs and cohort studies.

    ReviewPMID 35259334 ↗

  10. 10

    Enclomiphene raises testosterone while preserving fertility/semen parameters and is positioned as an alternative when exogenous testosterone (which suppresses LH/FSH and spermatogenesis) is unsuitable.

    ReviewEnclomiphene citrate for the treatment of secondary male hypogonadism.PMID 27337642 ↗

Last reviewed 2026-07-06 · Verified against PubMed · Educational, not medical advice